hi, just need some assistance as to where to place the step up in the 4-1 header i'm building.

header is 4-1, 1 5/8" from the engine then stepping up to 1 3/4 somewhere along the line. total length of the primaries is 34", car is daily driven, but regularly drag raced in the australian sport compact scene (and winning :D). rev limit currently sits at 7000rpm (*****!), but will be raised in the near future once the engine gets the rods and HC pistons sitting in my garage.

anyway, i've found out that most 4-1 steps happen between 1/2 - 2/3rds of the way along the primary - but which is best? is something closer to the engine better for high end power or is it closer to 2/3rds of the way along? on the flip side of that, whatever the result, can it be considered that if the step is closer to the engine, high end power is better and if the step is far away that is best for mid range power? dunno if that makes sense, but it is 10pm here...

thanks.

 

Contact burns stainless they can spec it for you, There is alot of engineering that goes into correctly designing a header

 

header is 95% designed. correct length is chosen, runners are within 1/2" of each other and the merge collector is sitting waiting to go, just need to try and find a little more info on where to place a step - that's one piece of information that's hard to find other than "somewhere between 1/2 and 2/3rds of the way along"